Been following this with interest. I would Definately be looking at the ecu. We know these motors shut down on high coolant temp. Urs is just shutting dow at a lower temp than programmed. As I understand it, fuel is not restricted, engine just won’t rev over 2k. When my engine got too hot, it would drive normally up to 2k revs then nothing. For some reason the ecu is not allowing any revs at all.
I have had experience of diesel pumps failing due to old age , wear and heat. For a good pump to fail due to heat alone it has to reach over 100 degrees. Had that problem on an air cooled diesel tractor. Also , as fuel and pump warms up if it’s worn, performance tapers off gradually on a purely mechanical pump and will keep running an engine even when they won’t start a cold engine without help from ether, or such. We know electronic chips are affected by heat, so to my mind it’s the ecu or the chip on the pump.
The bush fix is to install a lower temp thermostat or drill a series of holes around the skirt.4x6 mm holes will do it. Longer warm up times and lower running temp. No thermostat at all can cause problems of its own.
Or maybe none of the above, who knows with these things??